Surface Functionalization of Zinc Oxide by Carboxyalkylphosphonic Acid Self-Assembled Monolayers

Abstract

Two carboxyalkylphosphonic acids (HOOC(CH(2))(n)P(O)(OH)(2), n = 2 for 3-PPA and n = 9 for 10-PDA) have been deposited onto 1D zinc oxide (ZnO) nanowires and bare ZnO wafers to form stable self-assembled monolayers (SAMs). The samples were systematically characterized using wettability, atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). 3-PPA was bound to the ZnO surfaces mainly through the CO(2)H headgroup, and 10-PDA formed self-assembled monolayers on the nanoscaled ZnO surface through the PO(3)H(2) headgroups. To verify the potential utilization of the functionalized surfaces in the construction of biosensors or bioelectronics, IgG (immunoglobulin G) protein immobilization through SAM bridging was demonstrated. This work expands the application of phosphonic acid-based surface functionalization on sensing and optoelectronic devices.

Optical biosensors based on ZnO nanostructures: advantages and perspectives. A review

“…Cross linking between ZnO surface and protein via phosphoric groups is rarely used [91,57]. Comparing to silanization, it is more complicated process.…”

Spectroscopic and Theoretical Study of the Grafting Modes of Phosphonic Acids on ZnO Nanorods

“…14−17 Among mentioned metal oxides, nanostructured ZnO, a wide-band-gap semiconductor (E g = 3.37 eV at room temperature) 18 used in sensors, 19 electronic devices, 20,21 and solar cells, 22−24 is a promising substrate for the design of SAM-based organic− inorganic materials of technological relevance. 25−32 Examples of SAM-functionalized ZnO nanostructures include nanorods modified either with carboxyalkylphosphonic acids (HOOC-(CH 2 ) n P(O)(OH) 2 (n = 2, 9)) for biosensing 25 or with C60-functionalized phosphonic linkers for photonic devices 26 and nanowire-based ZnO field-effect transistors (FET) which use long-chain alkylphosphonic acids as gate dielectrics. 27 Despite various studies reported on a wide range of successful anchoring approaches, issues regarding preferred anchoring modes (monodentate, bidentate, tridendate, bridging bidentate, etc.)…”

Self-assembled thienylsilane molecule as interfacial layer for ZnO nanowire/polymer hybrid system

“…This result is consistent with the O 2 plasma-treated ZnO film reported by others. 25,31,32 Such hydroxylated treatment can promote the reactivity of ZnO sample with the silane reagent. After the silanization reaction, a WCA of 75 ± 2 deg [ Fig.…”